This invention relates to olefin copolymerization processes using substituted hafnocene catalyst compounds with noncoordinating anions.
Olefin polymers comprising ethylene and at least one or more (xcex1-olefin and optionally one or more diolefin make up a large segment of polyolefin polymers and will be addressed as xe2x80x9cethylene copolymersxe2x80x9d herein. Such polymers range from crystalline polyethylene copolymers to largely amorphous elastomers, with a new area of semi-crystalline xe2x80x9cplastomersxe2x80x9d in between. In particular, ethylene copolymer plastomers are now a well-established class of industrial polymers having a variety of uses associated with their unique properties, such as elastomeric properties and their thermo-oxidative stability. Uses of the plastomers include general thermoplastic olefins, films, wire and cable coatings, polymer modification (by inclusion in blends with other polyolefins), injection molding, foams, footwear, sheeting, functionalized polymers (such as by free-radical graft addition of polar monomers) and components in adhesive and sealant compounds.
Commercially prepared ethylene copolymers have been traditionally been made via Ziegler-Natta polymerization with catalyst systems largely based on vanadium or titanium. Newer metallocene catalyst compounds have received attention due to their ease of larger monomer incorporation and potential increases in polymerization activities. U.S. Pat. No. 5,324,800 describes metallocenes having substituted and unsubstituted cyclopentadienyl ligands which are suitable for producing high molecular weight olefin polymers, including linear, low density copolymers of ethylene with minor amounts of (xcex1-olefin.
Additionally, polypropylene is an important industrial polymer. To the extent that catalysts for these polymerizations can be improved, their use provides economic benefit.
Noncoordinating anions useful as catalyst components with such metallocenes are known. The term xe2x80x9cnoncoordinating anionxe2x80x9d is now accepted terminology in the field of olefin polymerization, both by coordination or insertion polymerization and carbocationic polymerization. The noncoordinating anions function as electronic stabilizing cocatalysts, or counterions, for cationic metallocenes which are active for olefin polymerization. The term xe2x80x9cnoncoordinating anionxe2x80x9d as used here and in the references applies both to noncoordinating anions and weakly coordinating anions that are not so strongly coordinated to the cationic complex as so to be labile to replacement by olefinically or acetylenically unsaturated monomers at the insertion site. U.S. Pat. No. 5,198,401 describes a preferred noncoordinating anion tetra(perflourophenyl) boron, [B(pfp)4]- or [B(C6F5)4]-, wherein the perfluorinated phenyl ligands on the boron makes the counterion labile and stable to potential adverse reactions with the metal cation complexes.
The utility of metallocene-based ionic catalysts in high temperature olefin polymerization is described in U.S. Pat. Nos. 5,408,017 and 5,767,208, EP 0 612 768, and WO 96/33227. Each addresses suitable metallocene catalysts for high temperature processes for olefin copolymerization. High molecular weight ethylene/xcex1-olefin copolymers is an objective of EP 0 612 768 and is addressed with catalyst systems based on bis(cyclopentadienyl/indenyl/fluorenyl) hafnocenes which are combined with an alkyl aluminum compound and an ionizing ionic compound providing a non-coordinating anion.
Improved catalyst systems for olefin polymerization are industrial useful.
The invention thus addresses specifically substituted, bridged hafnocene catalyst complexes activated with cocatalysts in which specific choices of catalyst and activator lead to unexpectedly high catalysis activities such that olefin cpolymers and copolymers can be prepared at surprisingly high production rates. More specifically, the invention relates tocatalysts for polymerizing olefins under supercritical or solution polymerization conditions at a reaction temperature at, or above, 60xc2x0 C. to 225xc2x0 C., or below. Specific monomers useful in the invention include ethylene and/or propylene and one or more comonomers capable of insertion polymerization with a hafnocene catalyst complex derived from A) a biscyclopentadienyl hafnium organometallic compound having i) at least one unsubstituted cyclopentadienyl ligand or aromatic fused-ring substituted cyclopentadienyl ligand not having additional substitutents on said ligand, ii) one substituted or unsubstituted, aromatic fused-ring substituted cyclopentadienyl ligand, and iii) a covalent bridge connecting the two cyclopentadienyl ligands where the bridge has a single carbon or silicon atom plus additional moities that complete carbon or silicon""s valence; and B) an activating cocatalyst, preferably a precursor ionic compound comprising a halogenated tetraaryl-substituted Group 13 anion and a carbenium cation.
This invention further relates to a metallocene catalyst system comprising an ion pair formed by contacting a metallocene and an activator wherein:
(a) the metallocene is described by the formula T(CpRn)(Cpxe2x80x2Rxe2x80x2m)HfQ2 wherein: (i) Cp and Cpxe2x80x2 are cyclopentadienyl ligands; (ii) Each R and Rxe2x80x2 are the same or different hydrocarbyl radicals having 1-20 carbon atoms; (iii) T is a bridge between Cp and Cpxe2x80x2, and comprises a substituted or unsubstituted methylene or silylene radical; (iv) each Q is a hydrocarbyl radical having 1-20 carbon atoms or is a halogen; (v) n is the number of hydrocarbyl substituents on Cp and n=0-4: (vi) m is the number of hydrocarbyl substituents on Cpxe2x80x2 and m=0-4; and (vii) wherein Cp, Cpxe2x80x2, R, Rxe2x80x2, m and n are selected such that CpRn is not equal to Cpxe2x80x2Rxe2x80x2m; and
(b) the activator is described by the formula: [Ar3C][NCA] wherein: (i) Ar is an aryl ligand; (ii) Ar3C is a triarylcarbenium; and (iii) NCA is a non-coordinating anion. In a preferred embodiment, the non-coordinating anion is represented by the formula: A(Ph*)3X wherein: (i) A is a Group-13 metalloid; (ii) Ph*is pentafluorophenylene radical; and (iii) X is alkyl-, alkylsily-, or halide-substituted phenyl or unsubstituted phenyl.
In a preferred embodiment, Rm is selected such that CpRm forms a fluorenyl or indenyl radical, preferably wherein the fluorenyl radical is disubstituted with t-butyl radicals and Rn is selected such that CpRn forms a substituted or unsubstituted cyclopentadienide radical.
Carbenium cations are cations in which carbon has a formal valence of 3 leaving it with a +1 charge. Such a species is highly lewis acidic and is a useful metallocene activator. Isoelectronic or isostructural cations in which the carbon is replaced with for example Si are also useful.
Cyclopentadienyl ligands: Cyclopentadienyl ligands are those ligands that have a cyclopentadiene anion core. These can be unsubstituted or substituted with hydrocarbyl groups as defined below. They can be part of fused-ring systems such as indenyl and fluorenyl. Similarly the use of hetero-atom containing cyclopentadienyl rings or fused rings, where a non-carbon Group 14, 15 or 16 atom replaces one of the ring carbons in the cyclopentadienyl ring or in a ring fused with the cyclopentadienyl ring is within the scope of cyclopentadienyl. The important component of a cyclopentadienyl ligand for this disclosure is that the ligand retain the aromatic, substantially planar, five-membered ring of the cyclopentadienide anion. The terms xe2x80x9cindenylxe2x80x9d and xe2x80x9cfluorenylxe2x80x9d ligands are therefore within the scope of cyclopentadienyl. When this disclosure wishes to refer to cyclopentadienide itself, it uses cyclopentadienide or cyclopentadine anion. See, for example, the teachings of WO 98/37106, having common priority with U.S. Ser. No. 08/999,214, filed Dec. 29, 1997, U.S. Pat. No. 6,451,938 and WO 98/41530, having common priority with U.S. Ser. No. 09/042,378, filed Mar. 13, 1998, now abandoned incorporated by reference for purposes of U.S. patent practice.
Cyclopentadienyl substitutions R and Rxe2x80x2, typically include one or more C1 to C30 hydrocarbon or hydrocarbylsilyl groups selected from linear, branched, cyclic, aliphatic, aromatic or combined structure groups, including fused-ring or pendant configurations. Examples include methyl, isopropyl, n-propyl, n-butyl, isobutyl, tertiary butyl, neopentyl, phenyl, n-hexyl, cyclohexyl, and benzyl.
In a preferred embodiment, T is a bridge with two aryl groups, each substituted with a C1-C20 hydrocarbyl or hydrocarbylsilyl group at least one of which is a linear C3 or greater substitutent. The bridge substituents preferably comprise C1-C20 linear or branched alkyl, or C1-C20 substituted-silyl, substituted phenyl groups, the alkyl or substituted-silyl substituents located in the para- or meta-positions of the aryl groups, preferably wherein at least one of said alkyl substituents is a C3 or higher linear n-alkyl substitutent, preferably C4 or higher. Specific examples include methyl, ethyl, n-propyl, n-butyl; sec-butyl, isobutyl, tert-butyl, n-pentyl, neopentyl, etc. In a preferred embodiment, T is CZZxe2x80x2 or SiZZxe2x80x2 wherein Z and Zxe2x80x2 are independently selected from substituted or unsubstituted alkyl or aryl moieties, preferably Z and Zxe2x80x2 are independently selected from trialkyl-substituted phenyl moieties, even more preferably Z and Zxe2x80x2 are independently selected from phenyl and 4-(triehylsilanyl)phenyl.
Q are hafnocene ligands that can be abstracted by the activator and are ligands that a olefin monomer can insert into as polymerization occurs. Q substituents specifically include fluorinated aryl groups, preferably perfluorinated aryl groups, and include substituted Q groups having substituents additional to the fluorine substitution, such as fluorinated hydrocarbyl groups. Preferred fluorinated aryl groups include phenyl, biphenyl, napthyl, and derivatives thereof. The disclosures of U.S. Pat. Nos. 5,198,401, 5,296,433, 5,278,119, 5,447,895, 5,688,634, 5,895,771, WO 93/02099, WO 97/29845, WO 99/43717, WO 99/42467 and copending U.S. application Ser. No. 09/261,627, filed 3 Mar. 1999, and its equivalent WO 99/45042 are particularly instructive as to suitable Q substituents and are incorporated by reference for purposes of U.S. patent practice.
Hydrocarbyl: For the purposes of this application the term xe2x80x9chydrocarbonxe2x80x9d or xe2x80x9chydrocarbylxe2x80x9d is meant to include those compounds or groups that have essentially hydrocarbon characteristics but optionally contain not more than about 10 mol. % non-carbon atoms, such as boron, silicon, oxygen, nitrogen, sulfur and phosphorous. xe2x80x9cHydrocarbylsilylxe2x80x9d is exemplified by, but not limited to, dialkyl- and trialkylsilyls.
Alkyl is a radical based on an aliphatic hydrocarbon. This backbone can be substituted by any number of other alkyl or aryl substituents as is known in the art.
Aryl is a radical based on an aromatic hydrocarbon. This backbone can be substituted by any number of other aryl or alkyl substituents as is known in the art.
NCA Is a non-coordinating ion. This term encompasses anions that are coordinating but only weakly so. The key is that incoming olefin monomer is capable of replacing NCA during a polymerization process.